Despite its charcoal color--and composition--this is not a bad egg. It's a good egg, a great egg, that attacks all the bad smells in your fridge. Charcoal eggs, sold here in sets of 4, slip one at a time into your refrigerator's egg crate to perform a job similar to a box of baking soda. Humidity control and odor absorption in a tighter, sexier package.
Charcoal eggs use natural activated carbon to inhale moisture and smells. It can also get rid of air and surface impurities, if you've ever seen charcoal products sold for water filtration and toothbrushing. In addition to the fridge, you can set eggs out around the house, in other areas of the kitchen, or in the bathroom, to achieve similar air-freshening effects.
Side Note: Ironically, one of the stanks the stank-absorbing charcoal egg could help suck up is that of another egg that looks a whole lot like it, but gives off wafts so traumatic your brain might make your nose lose its sense of smell if you sniff one: a century egg. OhsweetJesus these are eggs that have been planted in a Chinese recipe of clay, ash, salt, quicklime, and rice hulls for weeks, or even months. The fermentation process turns the yolk charcoal-ish and gelatinizes the white to a dark brown. Some new fun stuff present in the egg include salty jelly, hydrogen sulfide, and ammonia, so just take a guess how it smells.